DNS: From domain name resolution to network connectivity

DNS, or Domain Name System, is a key technology in the Internet, responsible for converting human-readable domain names into computer-understandable IP addresses. Although this seemingly simple process is often overlooked, it is one of the cornerstones of how the Internet operates. This article will provide an in-depth analysis of how DNS works, its place in the Internet architecture, and some important concepts related to DNS.

1. Basic working principle of DNS

The basic task of DNS is to translate domain names entered by users into corresponding IP addresses. This process includes the following steps:

1.1 local analyzer 查询

When a user enters a domain name into a browser, the operating system first checks the local DNS cache to see if the domain name has already been resolved. If there is a cache, the corresponding IP address will be returned directly; if not, the next query will be performed.

1.2 耒归查询

The local resolver sends a recursive query request to the local DNS server. The local DNS server may save a part of the DNS cache. If so, the IP address in the cache will be returned; otherwise, it means that a query needs to be made from a higher-level DNS server.

1.3 迭代查询

After the local DNS server receives the recursive query, it initiates an iterative query to the root DNS server. The root DNS server returns the IP address of the top-level domain (TLD). The local DNS server then sends a query request to the TLD server.

1.4 TLD 查询

When the TLD server receives a query request, it returns the IP address of the authoritative DNS server responsible for the top-level domain. The local DNS server then sends a query request to the authoritative DNS server.

1.5 Authoritative DNS query

Finally, after receiving the query request, the authoritative DNS server returns the IP address corresponding to the domain name. The local DNS server caches this IP address and returns the result to the user's local resolver, keeping a copy in its own cache.

2. The importance and role of DNS

DNS is known as the "phone book" of the Internet. Although users do not directly perceive its existence when using the Internet, it undertakes crucial tasks:

2.1 Address resolution and load balancing

While DNS resolves domain names into IP addresses, it can also achieve load balancing through domain name resolution. By configuring multiple different IP addresses for the same domain name, DNS can distribute user requests to different servers to achieve traffic balancing.

2.2 Network Troubleshooting and Fault Tolerance

When a server fails or is unavailable, the domain name is mapped to other available servers by modifying the DNS record to achieve rapid network failure switching and improve system availability and fault tolerance.

2.3 Security and Protection

DNS is also involved in network security. Domain name hijacking, DNS cache poisoning and other attack methods are directly related to DNS. By using secure DNS services and related security protocols, you can improve network security and prevent malicious attacks.

3. New developments and challenges of DNS

As the Internet continues to develop, DNS technology continues to evolve. Some new technologies and protocols, such as DNS over HTTPS (DoH) and DNS over TLS (DoT), aim to improve the privacy and security of DNS queries. At the same time, in the face of more complex network environments and more severe network security challenges, DNS technology also needs to be constantly innovated and strengthened.

Conclusion

As part of the Internet infrastructure, DNS plays a vital role in the normal operation of the Internet. It works silently behind the scenes, providing users with a convenient access experience. For developers and network administrators, knowing and understanding how DNS works is an important part of improving network performance and security. Through an in-depth understanding of DNS, we can better deal with various challenges on the Internet and ensure the smoothness and security of the network.